Merge two gathers — Geomage g-Platform™ User Manual

Merge two gathers

Merging/combining two seismic gathers (pre & post stack)

Theory

Merging seismic gathers requires matching geometry, sampling, amplitude, and phase so two datasets behave like a single continuous volume in both pre- and post-stack domains.

Pre-Stack Seismic Gathers (Shot / Receiver / CMP Gathers)

Purpose

Combine acquisition patches
Merge surveys from different vintages
Create continuous coverage before processing
Restore missing or incomplete gathers

Requirements / Steps

Match geometry

Match sampling parameters

Match trace headers

Match amplitude & phase

Sort to common domain
Example: sort both datasets to CMP gathers or shot gathers before merging.
Concatenate gathers

Post-Stack Seismic Gathers (2D/3D Volumes)

Purpose

Splicing two seismic lines
Merging 3D volumes from different surveys
Extending survey coverage
Time-lapse comparisons

Key Requirements

Coordinate alignment

Vertical consistency

Amplitude balancing

Phase consistency

Blending or Feathering

Grid Resampling

Final merge

3. Common Problems When Merging Gathers

Different CRS (UTM/WGS/Everest)
Different bin size or survey azimuth
Time shift mismatch
Phase mismatch
Amplitude mismatch
Different processing sequences
Overlapping zones with seams
Trace misalignment or geometry conflicts

4. QC After Merge

Check continuity of reflectors
Examine amplitude and phase consistency
Inline/crossline continuity
Histogram match
Spectrum match
Fold & coverage maps (pre-stack)

Input data

Input gather 1

connect/reference to the Output gather of 1st input gather

Input gather 2

connect/reference to the Output gather of 2nd input gather for merging

Parameters

Position of window { Constant, Variable }

select the options from the drop down menu.

Stitch position - provide the position where it should be merged.

Horizon item

in case the position of window is variable, then the user should provide the horizon. Connect/reference to the output horizon(s).

Layer (0-based)

by default, 0.

Window size

specify the position of the window size. By default, 100.

Interpolation params

this section deals with the horizon interpolation.

Map step X

provide the step size in x direction

Map step Y

provide the step size in y direction

Smooth window X

provide the smoothing window size in x direction

Smooth window Y

provide the smoothing window size in y direction

Interpolation type { ABOS, Kriging }

choose the interpolation type from the drop down menu. By default, ABOS.

Interpolation type - ABOS

Artificial Bounded Object Structure or ABOS is a specialized interpolation method where it uses an artificial bounded structure like network of polygons to model and interpolate the elevations information to create the topography map.

Interpolation type - Kriging

is a statistical interpolation method based on the assumption that the spatial data points are correlated. It creates an optimal surface that minimizes prediction errors by considering both the distance between data points and their spatial correlation.

Kriging covariance type { Exponential, Spherical, Gaussian }

select the kriging covariance type from the drop down menu.

Exponential

This can be used where the subsurface properties change abruptly over small distances.

Spherical

The Spherical model is useful when the data exhibits a more gradual spatial correlation up to a certain range and then behaves independently beyond that range. When subsurface structures have coherent properties within a certain distance but lose coherence at greater distances.

Gaussian

The Gaussian model is often applied in cases where there is a long-range, gradual spatial dependence between data points. It’s suitable for data where the spatial dependence does not drop off abruptly, such as when seismic properties gradually change over larger distances or in homogenous subsurface areas.

Kriging range

If two data points are closer than the kriging range, they are considered spatially correlated and will influence each other's estimated values. If the distance is greater than the range, their influence on each other will be ignored. If the distance between two data points is more than 500 then it assumes that the data beyond that limit there is no correlation

Kriging number of points

Total number of data points used to estimate/interpolate the unknown point/sample. The more the kriging points the better result however the computation time also increase with this.

Settings

Skip

By default, FALSE(Unchecked). This option helps to bypass the module from the workflow.

Output data

Output gather

generates the merged output gather.

Information

There is no information available for this module so the user can ignore it

Examples

In this example workflow, we are working on two post stack data sets. Both the datasets must have same number of channels/fffid/sps/, record length, sample interval etc.

In this exercise, we are applying a random noise attenuation procedure on one of the dataset and the 2nd dataset is having little noise in the shallow region. We would like to merge the random noise attenuated output with the 2nd input data at a certain time.

Also, in this workflow, we are covering both the options of constant and variable Position of the window. In case of the constant, it is a standard procedure of providing the time at which the merge takes place. In case of the variable, the user needs to provide the horizon information. Based on the horizon, it will perform the merging.

Constant

In the above example workflow, RNA output gather is considered as Input 1 & Read seismic traces module output gather is considered as Input 2.

Make the necessary references/connections to Merge two gathers modules.

Setup the parameters as per the requirement and execute the module.

Variable

In case of the variable position of the window, the user MUST provide the horizon information. If the user has an existing horizon then it can be called by using load item. Otherwise, the user has to pick the horizon using "Horizon picking" module and provide the output horizon to the Horizon item parameter.

Make the necessary reference/connections as mentioned in the previous section (Constant). Next go to parameters, and change the position of the window from Constant to Variable. Later, connect/reference the Horizon item to Output horizons of Horizon picking module.